Thermoplastic resin compositions

ABSTRACT

The thermoplastic resin composition according to the present invention comprises (A) about 20˜95 parts by weight of a rubber-modified polystyrene resin composed of (a 1 ) about 10˜60% by weight of a styrene-containing graft copolymer resin containing about 10˜60% by weight of a rubber and about 90˜40% by weight of a styrene-acrylonitrile copolymer, the styrene-acrylonitrile copolymer containing about 0.5˜10% by weight of acrylonitrile, and (a 2 ) about 90˜40% by weight of a styrene-containing copolymer resin containing 0˜20% by weight of a rubber; and (B) about 5˜80 parts by weight of a polyphenylene ether.

FIELD OF THE INVENTION

The present invention relates to a thermoplastic resin composition. Moreparticularly, the present invention relates to a thermoplastic resincomposition that comprises a rubber-modified styrene-containing resincontaining 0.5-10% by weight of acrylonitrile and a polyphenylene etherresin.

BACKGROUND OF THE INVENTION

Polyphenylene ether resin has good thermal resistance, high impactstrength, and good dimensional stability. However, polyphenylene etherresin has poor processability due to its excessively high thermalresistance. Therefore, the polyphenylene ether resin is blended with apolystyrene resin which has good compatibility with polyphenylene etherresin to improve processability for use of housing materials inelectrical apparatuses. However, the disadvantage could be observed thatthe blend of polyphenylene ether resin and polystyrene has poor impactstrength. In order to overcome the shortcoming, a rubber-reinforcedpolystyrene resin is used instead of polystyrene resin. However,although the impact strength of the resin composition is improved, theresin has decreased molding property and poor surface gloss.

U.S. Pat. No. 3,383,435 discloses blends of polyphenylene ether and oneor more styrene resins having improved processablity and chemicalresistance. Further, U.S. Pat. No. 4,360,618 discloses a polyphenyleneether blended with SAN or ABS polymers containing from 2˜8% by weight ofacrylonitrile. However, these resin compositions have insufficientappearance, impact strength, and molding property.

Accordingly, the present inventors have developed thermoplastic resincompositions which has a good surface gloss, impact strength, andmolding property by adding a rubber-modified styrene-containing resincontaining 0.5-10% by weight of acrylonitrile to a polyphenylene etherresin.

OBJECTS OF THE INVENTION

An object of the present invention is to provide thermoplastic resincompositions with good surface gloss, impact strength, and moldingproperty.

Other objects and advantages of this invention will be apparent from theensuing disclosure and appended claims.

SUMMARY OF THE INVENTION

A thermoplastic resin compositions according to the present inventioncomprise (A) 20˜95 parts by weight of a rubber-modifiedstyrene-containing resin composed of (a₁) 10˜60% by weight of astyrene-contajinig graft copolymer resin containing 10˜60% by weight ofa rubber and 90˜40% by weight of a styrene-acrylonitrile copolymer,wherein the styrene-acrylonitrile copolymer contains 0.5˜10% by weightof acrylonitrile, and (a₂) 90˜40% by weight of a styrene-containingcopolymer containing 0˜20% by weight of a rubber; and (B) 5˜80 parts byweight of a polyphenylene ether.

DETAILED DESCRIPTION OF THE INVENTION

(A) Rubber-Modified Styrene-Containing Resin

The rubber modified styrene-containing resin according to the presentinvention is a polymer wherein rubber phase polymers are dispersed inthe form of particles in a matrix obtained by polymerizing an aromaticvinyl monomer and a vinyl group containing monomer, which can bepolymerized therewith, in the presence of a rubber phase polymer. Suchrubber-modified styrene-containing resin is prepared by a known methodsuch as emulsion polymerization, suspension polymerization or bulkpolymerization, and is conventionally produced by an extrusion with astyrene-containing graft copolymer resin and a styrene-containingcopolymer resin. In a bulk polymerization, both a styrene-containinggraft copolymer resin and a styrene-containing copolymer resin areprepared together in one process. In other polymerizations, astyrene-containing graft copolymer resin and a styrene-containingcopolymer resin may be prepared separately. In either case, the contentsof rubber in a final rubber-modified styrene-containing resin to thetotal weight of the base resin are preferably in 5 to 30 parts byweight. Examples of such resins are acrylonitrile-butadiene-styrene(ABS) copolymer resin, acrylonitrile-acryl rubber-styrene (AAS)copolymer resin, acrylonitrile-ethylenepropylene rubber-styrene (AES)copolymer resin, and the like.

In this invention, the rubber modified styrene-containing resin (A) isprepared by mixing 10˜60% by weight of the styrene-containing graftcopolymer resin (a₁) with 90˜40% by weight of thy styrene-containingcopolymer resin (a₂).

(a₁) Styrene-Containing Graft Copolymer Resin

Examples of a rubber for styrene-containing graft copolymer resin arediene rubbers such as polybutadiene, poly(styrene-butadiene),poly(acrylonitrile-butadiene), etc; a saturated rubber in which hydrogenis added to said diene-containing rubber; isoprene rubber; a polybutylacrylic acid; and a terpolymer of ethylene-propylene-diene (EPDM). It ispreferable to use a diene-containing rubber, more preferably abutadiene-containing rubber. The content of rubber in the graftcopolymer-resign is preferably in the range of 10 to 60% by weight basedon the total weight of a graft copolymer resin.

Examples of aromatic vinyl-containing monomers are styrene, α-methylstyrene, p-methyl styrene, etc. In the above examples, styrene is themost preferable. At least one copolymerizable monomer may be introducedand applied to the aromatic vinyl monomers. It is preferred that thecopolymerizable monomer is a cyanide vinyl-containing compound such asacrylonitrile or an unsaturated nitrile-containing compound such asmethacrylonitrile.

The graft copolymer of the present invention is prepared bycopolymerizing 10˜60% by weight of rubber with 90˜40% by weight of themonomer mixture. The monomer mixture contains 90 to 99.5% by weight ofaromatic vinyl monomer such as styrene and 0.5 to 10% by weight ofunsaturated nitrile monomer. It is preferable that the monomer mixturecontains 93 to 99.5% by weight of aromatic vinyl monomer and 0.5 to 7%by weight of unsaturated nirtile monomer, more preferably 95 to 99% byweight of aromatic vinyl monomer and 1 to 5% by weight of unsaturatednirtile monomer.

In addition, in order to give good characteristics of processability andheat resistance, the monomers such as acrylic acid, methacryl acid,maleic anhydride and N-substituted maleimide can be added in the graftpolymerization. The amounts of the monomers are in the range of 0 to 40%by weight based on the styrene-containing graft copolymer resin.

To acquire good impact strength and surface appearance when saidstyrene-containing graft copolymer is prepared, the average size ofrubber particles is preferably in the range of from 0.1 to 0.5 μm.

(a₂) Styrene-Containing Copolymer Resin

The polystyrene resin of the present invention is prepared by emulsionpolymerization, suspension polymerization, bulk polymerization or acombination thereof For example, the polystyrene-containing resin isprepared by adding 80˜100% by weight of an aromatic alkenyl compounds,e.g. styrene or a mixture of aromatic alkenyl monomer and alkylestermonomer of an acrylic acid or a methacrylic acid: to 0˜20% by weight ofrubber selected from the group comprising of a butadiene rubber, anisoprene rubber, a copolymer of a butadiene and a styrene, and an alkylacrylate rubber and bulk-polymerizing by use of one of more initiatorsselected from the group consisting of benzoylperoxide, t-butylhydroperoxide, acetyl peroxide, and cumene hydroperoxide.

In the present invention, polystyrene which does not contain rubber orrubber-reinforced polystyrene may be used alone or in combination.

In this invention, the rubber modified styrene-containing resin (A) iscomposed of 10˜60% by weight of the styrene-containing graft copolymerresin (a₁) and 90˜40% by weight of the styrene-containing copolymerresin (a₂).

(B) Polyphenylene Ether Resin

The Polyphenylene ether resin is employed as a base resin to improveflame retardancy, heat resistance and rigidity of the resin compositionaccording to the present invention. As examples of the polyphenyleneether resin, poly(2,6-dimethyl-1,4-phenylene)ether,poly(2,6-diethyl-1,4-phenylene)ether,poly(2,6-dipropyl-1,4,-phenylene)ether,poly(2-methyl-6-ethyl-1,4-phenylene)ether,poly(2-methyl-6-propyl-1,4-phenyl)ether,poly(2-ethyl-6-propyl-1,4-phenylene)ether,poly(2,6-diphenyl-1,4-phenylene)ether, copolymer of poly(2,6-dimethyl-1,4-phenylene)ether andpoly(2,3,6-trimethyl-1,4-phenylene)ether, and copolymer ofpoly(2,6-dimethyl-1,4-phenylene)ether andpoly(2,3,5-triethyl-1,4-phenylene)ether can be used.

Preferably, copolymer of poly(2,6-dimethyl-1,4-phenylene)ether andpoly(2,3,6-trimethyl-1,4-phenylene)ether, andpoly(2,6-dimethyl-1,4-phenylene)ether are preferably used, morepreferably poly(2,6-dimethyl-1,4-phenylene)ether is used.

The degree of polymerization of polyphenylene ether is not limitedspecifically, but considering heat-stability or processability of theresin composition, it is preferable that the intrinsic viscosity ofpolyphenylene ether is in the range of from 0.2 to 0.8 when measured ina chloroform solvent at 25° C.

The content of the rubber-modified styrene-containing resin (A) used inthe present invention is 20˜95 parts by weight, more preferably, 40˜95parts by weight. The content of the polyphenylene ether resin (B) is5˜80 parts by weight, more preferably, 5˜60 parts by weight.

Other additives may be used in the thermoplastic resin compositions ofthe present invention. The additives include a flame retardant, ananti-dripping agent, an impact modifier, a plasticizer, an inorganicfiller, a heat stabilizer, an anti-oxidant, a compatibilizer, a lightstabilizer, and a pigment and/or a dye. The inorganic filler isasbestos, glass fiber, talc, ceramic, and sulphate. The additives areemployed in the amount of 0 to 50 parts by weight on the basis of 100parts by weight of the base resin.

The invention may be better understood by reference to the followingexamples that are intended for the purpose of illustration and are notto be construed as in any way limiting the scope of the presentinvention, which is defined in the claims appended hereto.

EXAMPLES

The components to prepare the thermoplastic resin compositions inExamples 1˜3 and Comparative Examples 1˜5 are as follows:

(A) Rubber-Modified Styrene-Containing Resin

(a₁) Styrene-Containing Graft Copolymer Resin

(a₁₁) Styrene-Containing Graft Copolymer Resin Containing 0% ofAcrylonitrile

50 parts of butadiene rubber latex powder, 50 parts of styrene and 150parts of deionized water were blended. To the blend, 1.0 parts ofpotassium oleate, 0.4 parts of cumenhydroperoxide, 0.2 parts ofmercaptan-containing chain transfer agent, 0.4 parts of glucose, 0.01parts of ferrous sulfate hydrate, and 0.3 parts of sodium pyrophosphatewere added. The blend was kept at 75° C. for 5 hours to obtain graftlatex. To the graft latex, 0.4 parts of sulfuric acid was added,coagulated and dried to obtain styrene-containing graft copolymer resincontaining 0% of acrylonitrile (a₁₁) in a powder form.

(a₁₂) Styrene-Containing Graft Copolymer Resin Containing 5% ofAcrylonitrile

50 parts of butadiene rubber latex powder, 47.5 parts of styrene, 2.5parts of acrylonitrile, and 150 parts of deionized water were blended.To the blend, 1.0 parts of potassium oleate, 0.4 parts ofcumenhydroperoxide, 0.2 parts of mercaptan-containing chain transferagent, 0.4 parts of glucose, 0.01 parts of ferrous sulfate hydrate, and0.3 parts of sodium pyrophosphate were added. The blend was kept at 75°C. for 5 hours to obtain graft latex. To the graft latex, 0.4 parts ofsulfuric acid was added, coagulated and dried to obtainstyrene-containing graft copolymer resin containing 5% of acrylonitrile(a₁₂) in a powder form.

(a₁₃) Styrene-Containing Graft Copolymer Resin Containing 15% ofAcrylonitrile

50 parts of butadiene rubber latex powder, 42.5 parts of styrene, 7.5parts of acrylonitrile, and 150 parts of deionized water were blended.To the blend, 1.0 parts of potassium oleate, 0.4 parts ofcumenhydroperoxide, 0.2 parts of mercaptan-containing chain transferagent, 0.4 parts of glucose, 0.01 parts of ferrous sulfate hydrate, and0.3 parts of sodium pyrophosphate were added. The blend was kept at 75°C. for 5 hours to obtain graft latex. To the graft latex, 0.4 parts ofsulfuric acid was added, coagulated and dried to obtainstyrene-containing graft copolymer resin containing 15% of acrylonitrile(a₁₃) in a powder form.

(a₁₄) Styrene-Containing Graft Copolymer Resin Containing 24% ofAcrylonitrile

50 parts of butadiene rubber latex powder, 38 parts of styrene, 12 partsof acrylonitrile, and 150 parts of deionized water were blended. To theblend, 1.0 parts of potassium oleate, 0.4 parts of cumenhydroperoxide,0.2 parts of mercaptan-containing chain transfer agent, 0.4 parts ofglucose, 0.01 parts of ferrous sulfate hydrate, and 0.3 parts of sodiumpyrophosphate were added. The blend was kept at 75° C. for 5 hours toobtain graft latex. To the graft latex, 0.4 parts of sulfuric acid wasadded, coagulated and dried to obtain styrene-containing graft copolymerresin containing 24% of acrylonitrile (a₁₄) in a powder form.

(a₂) Styrene-Containing Copolymer Resin

(a₂₁) GPPS (General Purpose Polystyrene)

GPPS by Cheil Industries Inc. of Korea (product name: HF-2680) with aweight average molecular weight of 210,000 was used.

(a₂₂) Rubber-Reinforced Styrene-Containing Resin (HIPS: High ImpactPolystyrene)

Rubber-reinforced styrene-containing resin by Cheil Industries Inc. ofKorea (product name: HG-1760S) containing 7% by weight of butadienerubber with a particle size of 0.4 μm was used.

(B) Polyphenylene Ether (PPE)

Poly(2,6-dimethyl-phenyl ether) by Asahi Kasei Co. of Japan (productname: P-402) was used.

(C) Phosphoric Acid Ester

Triphenylphosphate (TPP) with a melting point of 48° C. was used for aflame retardant.

The components (A), (B) and (C) as shown in Table 1 were blended andextruded in the form of pellets with a conventional twin-screw extruderat 200˜280° C. The pellets were dried at 80° C. for 3 hours and extrudedinto test specimens in a 6 oz. extruder at molding temperature of180˜280° C. and barrel temperature of 40˜80° C., and the resin pelletswere molded into test specimens. Impact strength of the test specimensof the Examples and Comparative Examples was measured according to Izodimpact strength ASTM D-256 (⅛″ notched). Melt Flow index(g/10 min) wasmeasured according to ASTM D-1238(220° C., 10 kg). Gloss was measuredaccording to ASTM D-523 with a 60 degrees viewing angle. The testresults are shown in Table 1. TABLE 1 Examples Comparative Examples 1 23 1 2 3 4 5 (a₁₁) — — — 20 — — — — (a₁₂) 20 20 20 — — — — — (a₁) (a₁₃) —— — — 20 — — — (A) (a₁₄) — — — — — 20 — — (a₂₁) 25 50 — 25 25 25 70 —(a₂) (a₂₂) 25 — 50 25 25 25 — 70 (B) 30 30 30 30 30 30 30 30 (C) 10 1010 10 10 10 10 10 Gloss (%) 94 95 93 95 90 85 97 90 Izod Impact 35 30 3830 25 23 14 20 strength (⅛″) Melt Flow 33 35 30 25 25 20 45 25 Index(g/mL)

As shown in Examples 1˜3, the resin composition of the present inventionhad good impact strength and surface gloss due to styrene-containinggraft copolymer resin containing 5% of acrylonitrile (a₁₂). As shown inComparative Examples 4˜5, the resin compositions which do not containstyrene-containing graft copolymer resin (a₁) show good gloss, but poorimpact strength. Comparative Example 1 employing styrene-containinggraft copolymer resin containing 0% of acrylonitrile (a₁₁) showed lowmelt flow index. Comparative Examples 2˜3 employing styrene-containinggraft copolymer resin containing more than 15% by weight ofacrylonitrile showed poor impact strength. As described above, the resincomposition of the present invention can obtain good mechanicalproperties and surface gloss by adding styrene-containing graftcopolymer resin containing 0.5-10% of acrylonitrile.

The present invention can be easily carried out by an ordinary skilledperson in the art. Many modifications and changes may be deemed to bewith the scope of the present invention as defined in the followingclaims.

1. A thermoplastic resin compositions comprising: (A) 20˜95 parts byweight of a rubber-modified styrene-containing resin composed of (a₁)10˜60% by weight of a styrene-containing graft copolymer resincontaining 10˜60% by weight of a rubber and 90˜40% by weight of astyrene-acrylonitrile copolymer, wherein the styrene-acrylonitrilecopolymer contains 0.5˜10% by weight of acrylonitrile, and (a₂) 90˜40%by weight of a styrene-containing copolymer resin containing 0˜20% byweight of a rubber; and (B) 5˜80 parts by weight of a polyphenyleneether.
 3. The thermoplastic resin compositions as defined in claim 1,wherein said styrene-containing copolymer resin (a₂) is selected fromthe group consisting of a polystyrene, a rubber-reinforced polystyrene,and a mixture thereof.
 4. The thermoplastic resin compositions asdefined in claim 1, wherein said polyphenylene ether resin (B) ispoly(2,6-dimethyl-1,4-phenylene)ether.
 5. The thermoplastic resincompositions as defined in claim 1, wherein said a styrene-containinggraft copolymer resin (a₁) contains 0.5˜7% by weight of acrylonitrile.6. The thermoplastic resin compositions as defined in claim 1, whereinsaid a styrene-containing graft copolymer resin (a₁) contains 1˜5% byweight of acrylonitrile.
 7. The thermoplastic resin compositions asdefined in claim 1, wherein said resin composition comprises 40˜95 partsby weight of rubber-modified styrene-containing resin (A) and 5˜60 partsby weight of polyphenylene ether (B).
 8. The thermoplastic compositionsas defined in claim 1, wherein said resin composition further comprisesa flame retardant, an anti-dripping agent, an impact modifier, aplasticizer, an inorganic filler, a heat stabilizer, an anti-oxidants, alight stabilizer, a pigment, and/or a dye.